Research and Analysis of Pollution Indicators in Marine and Coastal Ecosystems along the Southern Black Sea Coast

Key pollution indicators have been studied to assess the ecological status of marine and coastal ecosystems along the Southern Black Sea coast. Three aquatic ecosystems were covered: a lake (Burgas Lake), a river (the mouth of the Karaagach River), and a marine ecosystem (Burgas Bay). In situ measurements and laboratory analyses of water and sediment were conducted at nine sites on a monthly basis during 2022–2023. The focus is on microplastics and toxic metals/metalloids. For the first time in the region, a quantitative and qualitative analysis of microplastics was performed, revealing changes in the composition, number, and surface area of particles (MPs/dm³; MPs/kg). The most frequently detected types are PE, PET, and PVC. The analysis of toxic metals/metalloids showed elevated levels of Al, Pb, Ni, Cd, and Mn in Burgas Lake and the Karaagach River, with a seasonal pattern. The developed methodology for extracting and analyzing microplastics from different matrices (water and sediment) is a contribution toward future standardization in scientific and applied practice. The results can serve as a basis for monitoring, preventive measures, and educational initiatives.